3l5 On the Colouring Principle of Lapis Lazuli. 



prodaced no fenfible effect; next day, twelve drops induced 

 a {light propenfity to deep ; and the day following, eighteen 

 drops rendered this propenfity ftill greater. By thus adding 

 {ix drops to the dofe every fucceeding day, always with fugar, 

 he fwallowed half a grain on the fixth day, which produced 

 a profound tranquillity and neceffity of {leep. 



It is recommended to thofe who employ this remedy to 

 ufe pure acetous ether ; but it is to be obfer\ed, that it is not 

 eijfily met with in that ftate. The following is the procefs 

 f;>r preparing it, prefcribed by C. Sedillot : 



Take equal parts (for example, a pound) of alcohol, and 

 another of acetous acid. Diflil this mixture in a glafs re- 

 tort, and the refult will be the acetous ether; which mufl 

 be reiiified to free it from the fuperabundant acid which has 

 paffed over with it in diftillation. For this purpofe put it 

 into a glafs vefTel, into which introduce a folution of the car- 

 bonat of pot-afli (fait of tartar): this alkali abforbs the acid, 

 and the ether floats on the furface. It is then decanted, and 

 reftiiied by a new diftillation in a glafs retort with a fuitable 

 apparatus. 



V. 0?i the Kature of the Cplouring Principle of Lapis Lazuli. 

 Bv C. GUVTON*. 



c 



HEMISTS have long made that blue ftone, known 

 under the name of lapis lazuli, an objeft of their refearch, 

 ■with a view, in particular, to difcover the colouring fubftance 

 which gives it fo high a value; on account of the fplendour 

 it communicates to works in which it is employed, and of 

 the ultramarine, fo much elkcmed in painting, which is 

 preoared from it. This colour v*as firlt afcribed to copper; 

 but the celebrated JSlargraf demonftrated the fallacy of this 

 opinion, as he found in it onlv filex, fulphat of lime, lime, 

 and a little iron. Some after him fufpe6i;ed in it the prefcnce 

 of the oxyd of cobalt; and others, fuch as Kinmann, a little 

 fluoric acid : but aH tbefe coujefturcs, by a more accurate 

 examination, were foon fliown to be falfe. 



* From x\\c A.nal.s dc Chime, No. loo. 



The 



